1. Field of the Invention
The present invention relates to a device for controlling a switch operated by a spring, for example, a breaker in a switching device for an electric power unit installed in a transforming station and a switchyard.
2. Discussion of Background
Generally, a spring is utilized as an origin of force for operating a control device of a breaker as a switch. FIGS. 14 through 19 illustrate a conventional spring controlling device of a breaker disclosed in, Japanese Unexamined Patent Publication No. JP-A-63-304542, wherein FIG. 14 is a perspective view, and FIG. 15 illustrates a structure of an important portion of the controlling device.
FIG. 16 illustrates a state of the spring controlling device in a state that the conventional breaker is opened. FIG. 17 illustrates a state of a torsion bar in a released state. FIG. 18 is a front view of the conventional breaker. FIG. 19 is a characteristic diagram illustrating a relationship between a displacement of a breaking control unit and a gas pressure in a cylinder in the conventional breaker.
In these figures, numerical reference 101 designates a casing; numerical reference 124 designates a cylinder fixed to the casing 101; and numerical references 26, 27 designate levers rotatably engaged with pins (not shown) located on an end surface of the casing 124.
Numerical reference 28 designates a torsion bar for opening a circuit, one end of which is fixed to the casing 101 and the other end thereof is fixed to the lever 26. Numerical reference 34 designates a torsion bar for opening the circuit, one end of which is fixed to the lever 26 and the other end thereof is fixed to a rotation shaft 32. Numerical reference 29 designates a torsion bar for closing the circuit, one end of which is fixed to the casing 101 and the other end thereof is fixed to a lever 27. Numerical reference 35 designates a torsion bar for closing the circuit, one end of which is fixed to the lever 27 and the other end thereof is fixed to a rotation shaft 33.
The conventional device will be described mainly in reference of FIG. 15. Numerical reference 37 designates a making lever fixed to the rotation shaft 33, which rotation shaft 33 is fixed to an end of the torsion bar 35 to give a rotational force in the counterclockwise direction by the torsion bars 29, 35 for closing the circuit as illustrated in FIG. 14. Numerical reference 2 designates a cam shaft supported by the casing 101; and numerical reference 3 designates a cam attached to the cam shaft 2. Numerical reference 13 designates a pin provided in the cam 3 for engaging a making latch; numerical reference 14 designates a making latch engaged with the pin 13 for engaging the making latch 13; and numerical reference 15 designates a making trigger engaged with the making latch 14. Numerical reference 16 designates a making electromagnet having a plunger 17.
Numerical reference 38 designates a rotation shaft supported by the casing 101, which rotation shaft is driven in the counterclockwise direction in FIG. 15 by a motor (not shown) Numerical reference 39 designates a pinion fixed to the rotating shaft 38; and numerical reference 40 designates a gear fixed to the cam shaft 2 so as to be engaged with the pinion 39, wherein teeth of the large gear are partially removed so as to be disengaged with the pinion 39 when the torsion bars 29, 35 for closing the circuit illustrated in FIG. 14 are prestressed. Numerical reference 41 designates a link for connecting the making lever 37 to the gear 40.
Numerical reference 36 designates a breaking lever fixed to the rotation shaft 32 connected to an end of the torsion bar 34 for opening the circuit formed to receive a rotational force in the counterclockwise direction by the torsion bars 28, 34 for opening the circuit illustrated in FIG. 14. Numerical reference 8 designates a releasing latch engaging pin provided in the breaking lever 36; and numerical reference 9 designates a roller provided in the breaking lever 36. Numerical reference 18 designates a releasing latch engaged with the releasing latch engaging pin 8.
Numerical reference 19 designates a releasing trigger engaged with the releasing latch 18. Numerical reference 20 designates a releasing electromagnet having a plunger 21. Numerical reference 22 designates a movable contact of the breaker, which contact is connected to the breaking lever 36 through a linkage mechanism 23 and a rod 61. The movable contact 22 and the rod 61 of the breaker will be described in detail in a latter part of this paragraph in reference of FIG. 18. Numerical reference 42 designates a buffer connected to the breaking lever 36 provided to relax an impact caused at a time of opening and closing the movable contact 22.
An operation of opening the circuit will be described. The breaking lever- 36 is constantly applied with a rotational force in the counterclockwise direction in FIG. 14 by the torsion bars 28, 34 for opening the circuit, which rotational force is retained by the releasing latch 18 and the releasing trigger 19. Under this state, when the releasing electromagnet 20 is excited, the plunger 21 is rightward moved to thereby release an engagement of the releasing latch 18 with the releasing trigger 19 by a clockwise rotation of the releasing trigger 19.
When the engagement between the releasing trigger 19 and the releasing latch 18 is released, the releasing latch 18 rotates in the counterclockwise direction by a counterforce received from the releasing latch engaging pin 8, whereby the releasing latch 18 is disengaged with the releasing latch engaging pin 8. The breaking lever 36 rotates in the counterclockwise direction to resultantly move the movable contact 22 in the direction of opening the circuit through a linkage mechanism 23 connected to the breaking lever 36. FIG. 16 illustrates a state after completing this operation of opening the circuit.
In the next, an operation of closing the circuit will be described. In FIG. 16, the cam 3 is connected to the making lever 37 through the cam shaft 2, the gear 40 fixed to the cam shaft 2, and the link 41, wherein the gear 40 and the cam 3 are applied with a rotational force in the clockwise direction by the torsion bars 29, 35 for closing the circuit. This rotational force is retained by the making latch 14 and the making trigger 15, which will be described in a latter part of this paragraph. Under this state illustrated in FIG. 16, when the making electromagnet 16 is excited, the plunger 17 is moved in the right direction; the making trigger 15 is rotated in the clockwise direction; and an engagement of the making latch 14 with the making trigger 15 is released.
When the engagement between the making trigger 15 and the making latch 14 is released, the making latch 14 rotates in the counterclockwise direction by a counterforce received from the making latch engaging pin 13. Therefore, the cam 3 rotates in the clockwise direction by a releasing force of the torsion bars 29, 35 for closing the circuit. Because an end portion of the cam 3 lifts the roller 9 located in the breaking lever 36, the breaking lever 36 is moved in the clockwise direction, i.e. an arrow A in FIG. 23 while twisting the torsion bars 28, 34 for opening the circuit, whereby the torsion bars 28, 34 for opening the circuit are prestressed.
When the breaking lever 36 is rotated to arrive a predetermined position, the releasing latch engaging pin 8 is engaged with and held by the releasing latch 18. The operation of closing the circuit is completed under a state illustrated in FIG. 17. As illustrated in FIG. 17, just after completing the operation of closing the circuit, the torsion bars 29, 35 are released. Because the torsion bars 28, 34 for opening the circuit are prestressed by releasing the torsion bars 29, 35 for closing the circuit, a prestressed energy of the torsion bars 29, 35 for closing the circuit is made larger than an energy required for prestressing the torsion bars 28, 34 for opening the circuit.
An operation of prestressing the torsion bars 29, 35 for closing the circuit will be described in reference of FIG. 17. By driving the pinion 39 in the counterclockwise direction in FIG. 17 by a motor (not shown), the gear 40 is rotated in the clockwise direction; the rotation shaft 33 is rotated in the clockwise direction via the link 41 and the making lever 37, whereby the torsion bars 29, 35 are prestressed.
The cam shaft 2 is applied with a rotational force in the clockwise direction by a force of releasing the torsion bars 29. 35 for closing the circuit through the link 41 at a position after a dead point where a direction of pulling the link 41 overlaps a center of the cam shaft 2. Simultaneously, because teeth of the large gear 40 are partially removed, an engagement between the pinion 39 and the gear 40 are disengaged, and the cam coaxially fixed to the large gear 40 rotates in the clockwise direction.
Thus, when the cam 3 rotates to arrive a predetermined position, the making latch engaging pin 13 is engaged with the making latch 14; a rotational force of the gear 40 in the clockwise direction applied by the torsion bars 29, 35 for closing the circuit is retained, whereby an operation of prestressing is completed. Consequently, the torsion bars 28, 34 for opening the circuit and the torsion bars 29, 35 for closing the circuit are returned again to the prestressed state illustrated in FIG. 15.
In the next, the breaker itself will be described. FIG. 18 is a front view of the breaker. The linkage mechanism 23 includes a lever 60, a link 62, a supporting plate 63, and a rotation shaft 88. The rotation shaft 88 is rotatably supported by the supporting plate 63; and the lever 60 is fixed to the rotation shaft 88 so as to rotate along with the rotation shaft 88. Another rotatable lever fixed to the rotation shaft 88 is connected to the link 62 via a pin.
The casing 101 of the device for controlling spring is fastened to the supporting plate 63, which is fastened to a right cover 64a of a pressure vessel 64. The breaking lever 36 of the spring controlling device is connected to the lever 60 fixed to the rotating shaft 88 via the rod 61. A high pressure gas 72 for electrically insulating is encapsulated in the pressure vessel 64. The pressure gas is for example a sulfurhexafluoride. Numerical reference 68 designate supporting tables fixed to the pressure vessel 64; numerical reference 67 designates a piston fixed to the supporting table 68 located in the right side; and numerical reference 71 designates a cylinder.
The movable contact 22 has a movable contact 22a, moved by the spring controlling device, and a nozzle 22b. Numerical reference 70 designates a fixed contact supported by the supporting plate 68 located in the left. A breaking control unit 69 includes the movable contact 22 and the cylinder 71, which breaking control unit 69 is connected to the breaking lever 36 of the spring controlling device via an insulating rod 66, a shaft 65, the linkage mechanism 23 and the rod 61 so as to be moved.
When the breaker is closed, the movable contact 22a, the nozzle 22b, and the fixed contact 70 are in contact. The movable contact 22 and the fixed contact 70 are a make break contact in a gas according to the present invention.
In a process that the breaker is opened, the breaking control unit 69, specifically the movable contact 22 and the cylinder 71 linearly move in the right direction in FIG. 18 at a high rate, whereby a pressure of the cylinder 71 becomes several times as high as that in a steady state. This high pressure gas generates a high speed gas flow toward an arc generated between the nozzle 22b and the fixed contact 70 when the breaking control unit 69 is released from the fixed contact 70 to thereby cool the arc and suppress the ark with a large current.
In this process, the high pressure in the cylinder 71 works as a counterforce against a movement of the breaking control unit 69, i.e. releasing force generated by the torsion bars 28, 34 for opening the circuit in the spring controlling device. FIG. 19 is a graph for showing a relationship between a displacement of the breaking control unit 69 with respect to a lapse of time and a gas pressure in the cylinder 71 in the conventional technique, wherein a solid line Pa designates the pressure in the cylinder 71; and a solid line S designates the displacement of the movable contact 22. Further, dotted lines Pa2, S2 respectively designate the gas pressure in the cylinder 71 and the displacement of the movable contact 22 when it is presumed that the counterforce is small.
Because, in actuality, the counterforce is large, even though it is required to quickly cut the arc by increasing the gas pressure in the cylinder 71 of the breaking control unit 69 at a latter stage of the displacement of the movable contact 22 as the dotted line Pa2, the counterforce against the driving force of the spring controlling device becomes large and the gas pressure cannot be increased, whereby a sufficient gas flow can not be secured as a solid line Pa.
When the conventional device for controlling spring is applied with a large electric power, it is necessary to increase releasing force by increasing an angle of twist of a torsion bar. Because there is an upper limit of strength in the angle of twist, it is necessary to extend the torsion bar. Further, because a load applied to constitutional components is increased when the electric power is increased, whereby it is also necessary to make the components large for assuring the strength. Thus, when the device for controlling spring deals with a high electric power, there is a problem that the weight of movable portions is increased and an entire spring controlling device became large.
When the spring controlling device deals with a high electric power, it is necessary to increase the force of spring of a torsion bar and therefore a load applied to the casing 101 and the cylinder 124 is increased. Therefore, if the rigidity of the casing is insufficient, the casing is deformed and a distance between the components is changed, whereby the device does not normally operate. As a countermeasure, it is necessary to increase the strength of the casing, whereby there are problems that the casing becomes large and the weight thereof is increased.
Further, because a rotational force of the torsion bars 28, 34 for opening the circuit in the conventional spring controlling device is decreased as a linear function with respect to a rotational angle of the breaking lever 36, force applied to the movable contact 22 decreases in accordance with a change approximate to the linear function. Accordingly, when the pressure in the cylinder 71 of the breaking control unit 69 is increased in a latter stage of the displacement of the movable contact 22, the rotational force of the torsion bars 28, 34 for opening the circuit unfavorably decrease. Therefore, there are problems that a gas flow sufficient for cooling the arc is not produced by increasing the pressure in the cylinder 71 at a time of breaking and a performance of breaking is restricted.